Coordinate Transformation (LL + Elevation to WGS84)

Question

I'm currently working on a 3D visualization project, and I came across an issue that I noticed we've been doing in a hackish way.

I'm not too experienced with the WGS84 system itself, and I was wondering if there was a "correct" way to convert a LL point into the WGS coordinate, given a specific value of elevation above the Earth's orbit.

How we're doing it now is doing the usual conversion from LL to WGS84, then taking the unit vector of that, and multiplying it by the sum of the elevation and the Earth's radius. This doesn't seem like the most efficient method, and I'm wondering if there's a more accepted way to make that conversion.

Answer 1

Many projection libraries, such as Proj.4 and libraries using it like GDAL/OGR will allow you to specify an elevation.

The EPSG project has a database that lists the "proper" way to implement this, for nearly every projection out there, including WGS84 in geographic and projected coordinate systems. It is a freely available database (although in MS Access format).